Portion of a humidifier tub



FIG. 1 is a front perspective view of a portion of a humidifier tub for a respiratory apparatus according to our design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a top view thereof; and,

FIG. 5 is a right side view thereof, with the left side view thereof being a mirror image thereof.

Throughout the various figures of the drawings, certain views may not be provided. The omission of a particular view is intended to convey that the element(s) depicted is/are plain and unornamented in that omitted view, or that the particular ornamental appearance in that view is simply not claimed.

Where included, broken lines showing environment or structure are for illustrative purposes only and form no part of the claimed design. Where included, dotted lines represent the border between claimed and non-claimed subject matter and form no part of the claimed design. 

The ornamental design for a portion of a humidifier tub, as shown and described. 